In recent years, in mobile devices such as portable televisions, mobile telephones, smartphones, MP3 players, and automotive navigation systems, it is desirable for moving images, still images, and the like to be displayed in a larger display screen without increasing the size of the mobile device itself.
As a display device installed in such a mobile device, a liquid crystal display device is in general use due to being energy-saving, thin, light-weight, and the like, in addition to the high productivity of liquid crystal display devices.
However, in conventional liquid crystal display panels included in liquid crystal display devices, there were limits to how large the display region of the liquid crystal display panel could be made, or in other words, how narrow the frame region, which is a non-display region, could be made, due to the following problems.
FIG. 17(a) shows a frame region in a conventional liquid crystal display panel, and FIG. 17(b) shows a width of a sealing material formed in the frame region of the liquid crystal display panel shown in FIG. 17(a) at the time of drawing compared to the width of the sealing material after both substrates have been bonded together.
As shown in FIG. 17(a), a liquid crystal display panel 100 includes a color filter substrate 101 and an active matrix substrate 108 disposed facing each other.
In a non-display region (frame region) R1 of the liquid crystal display panel 100, a black matrix layer 102 and an overcoat layer 104 are layered in this order on the color filter substrate 101.
On the other hand, in a display region R2 of the liquid crystal display panel 100, the black matrix layer 102 is formed in a grid pattern on the color filter substrate 101, color filter layers 103 of respective colors (red, blue, green) are formed on the black matrix layer 102 formed in a grid pattern, and the overcoat layer 104 is formed covering the color filter layers 103 of the respective colors.
A common electrode layer (not shown in drawings) made of a transparent conductive material such as ITO (indium tin oxide) is formed on the overcoat layer 104 in the non-display region R1 and the display region R2 of the liquid crystal display panel 100, and photospacers 105 for maintaining a uniform distance (cell gap) between the color filter substrate 101 and the active matrix substrate 108 are formed on the common electrode layer.
An alignment film (not shown in drawings) is formed on the topmost layer of the color filter substrate 101.
On the other hand, in the display region R2 portion of the active matrix substrate 108 of the liquid crystal display panel 100, a plurality of TFT elements, a plurality of signal lines, pixel electrodes made of a transparent conductive material such as ITO formed for respective pixels, and an alignment film are formed, although these are not shown in the drawings.
In general, a drawing device such as a dispenser device is used to form a sealing material 107 in a frame shape in the periphery of the color filter substrate 101, and after liquid crystal 106 is dripped into the inner side of the sealing material 107, the color filter substrate 101 and the active matrix substrate 108 are bonded together.
As shown in FIG. 17(b), when the sealing material 107 is formed using a drawing device such as a dispenser device, undulations occur in the drawn sealing material 107 due to variations resulting from various causes such as vibration during drawing, output pressure, and the height of the output hole.
The cross-sectional area of the sealing material 107 drawn by such a drawing device generally has a variation of approximately 10% to 30%. When the color filter substrate 101 and the active matrix substrate 108 are bonded together using the sealing material 107 formed in this manner, the variation in cross-sectional area directly results in variation in the width direction of the sealing material 107 (left and right direction in the drawing), thus resulting in even larger undulations in the sealing material 107.
In other words, when forming the sealing material 107 using a drawing device such as a dispenser device, the output amount of the sealing material 107 varies due to the above-mentioned reasons, and variation occurs in the width direction (left and right direction) and the height direction of the sealing material 107. As a result, as shown in FIG. 17(b), when bonding together the color filter substrate 101 and the active matrix substrate 108, variation also occurs in the width (107L, 107R) of the sealing material 107 spreading in the left and right direction in the drawing.
In such a conventional configuration, a relatively large variation occurred in the width of the sealing material 107 formed in the non-display region R1 (frame region), and therefore, it was difficult to realize a narrower frame in the liquid crystal display panel because the width of the non-display region R1 (frame region) depended on this variation.
More specifically, FIG. 17(a) shows a frame region in one out of a plurality of liquid crystal display panels 100 attained by separating a panel that includes a plurality of liquid crystal display panels 100 and that has a large display region R2 relative to the outer shape of the panel. If the sealing material 107 spreads to the separation line that separates the panel having a large display region R2 relative to the outer shape of the panel into the plurality of liquid crystal display panels 100, this causes a worsening of the separation property. Thus, it is necessary to provide a margin region of a certain width, but if there is relatively large variation in the width of the sealing material 107 as in the conventional configurations, then the margin region of a certain width has to be made wide, thus presenting a difficulty in narrowing the frame of the liquid crystal display panel.
Thus, techniques to mitigate variation in the width of the sealing material 107 formed in the non-display region R1 (frame region) such as that mentioned above have been studied since before.
For example, Patent Document 1 discloses a configuration in which a groove that defines the width of the sealing material 107 is formed on an insulating film provided in a liquid crystal display panel.
FIG. 18(a) shows a schematic configuration of the liquid crystal display panel disclosed in Patent Document 1.
As shown, the liquid crystal display panel includes an opposite substrate 202 provided with an opposite electrode 201, and a pixel substrate 204 provided with pixel electrodes 203. The inner surfaces of the respective substrates where the opposite electrode 201 and the pixel electrodes 203 are formed face each other, and the opposite substrate 202 and the pixel substrate 204 are bonded together through a sealing material 205.
The sealing material 205 is formed in a frame on the four sides of the liquid crystal display panel, which constitute the non-display region of the liquid crystal display panel, surrounding the display region where a plurality of pixels provided in the liquid crystal display panel are arranged.
Liquid crystal 206 is sealed between the opposite substrate 202 and the pixel substrate 204.
A gate electrode 209, a gate insulating film 207g (insulating film 207 in the non-display region), a semiconductor film 210, a source electrode 211, a drain electrode 212, and a protective insulating film 213 constitute a thin film transistor 208 formed on the pixel substrate 204, and the drain electrode 212 of the thin film transistor 208 and the pixel electrode 203 are electrically connected to each other.
In the insulating film 207 formed in the non-display region of the liquid crystal display panel, a groove 207a having a width corresponding to the width of the sealing material 205 provided on the substrate by silkscreen printing, a dispenser device, or the like is formed, and as a result of the groove 207a, when the opposite substrate 202 and the pixel substrate 204 are bonded together, the width to which the sealing material 205 spreads can be defined, thus allowing the frame of the liquid crystal display panel to be narrowed to a certain extent.
Patent Document 2 discloses a configuration in which a first overcoat film is provided on an active matrix substrate of a liquid crystal display panel in order to flatten the surface, and a groove for disposing a sealing material therein is formed in the first overcoat film in a frame shape.
FIG. 18(b) shows a schematic configuration of the liquid crystal display panel disclosed in Patent Document 2.
As shown, an active matrix substrate 320a and an opposite substrate 330a, which face each other, are included in the liquid crystal display panel 350a, and a liquid crystal layer 325 and a sealing material 324 provided surrounding the liquid crystal layer 325 are provided between both substrates 320a and 330a. 
The active matrix substrate 320a includes an insulating substrate 310a, a thin film transistor array that includes a plurality of gate wiring lines 311 provided on the insulating substrate 310a, a first overcoat film 312 provided as a planarizing film that covers the thin film transistor array, a plurality of pixel electrodes 313 provided in a matrix on the first overcoat film 312, and an alignment film 314a provided covering the respective pixel electrodes 313.
On the other hand, the opposite substrate 330a includes an insulating substrate 310b, a black matrix 316 provided in a grid pattern on the insulating substrate 310b, a plurality of colored layers 317 respectively colored red (R), green (G), or blue (b) and provided between the respective grids of the black matrix 316, photospacers 315 provided in a columnar shape over the respective colored layers 317 overlapping the black matrix 316, a second overcoat film 318 provided as a planarizing film covering the respective colored layers 317, a common electrode 319 provided on the second overcoat film 318, and an alignment film 314b provided covering the common electrode 319.
As shown, in a non-display region F (frame region), which is a region peripheral to a display region D in the liquid crystal display panel 350a, a groove 312a for disposing a sealing material 324 therein is formed in the first overcoat film 312 in a frame shape along the region where the sealing material 324 is to be formed.
According to the configuration above, it is possible to reliably form the sealing material 324 in a prescribed region in the liquid crystal display panel 350a, thus allowing the frame of the liquid crystal display panel 350a to be narrowed.